The concept of hidden curriculum has become well established. It addresses the contexts of learning, the actions of students' peers and teachers, and other domains which shape learning but are not part of official syllabuses. The concept of a hidden marketplace for private tutoring, widely known as shadow education, is less established but also becoming part of general understanding of the complementarities of regular and supplementary instruction. This paper brings the two literatures together to examine the values transmitted, mostly unintentionally, by shadow education in Cambodia. Most of this shadow education is delivered by regular teachers, commonly to their existing students and in their existing schools. The paper considers the impact of shadow education not only on the students who do receive it but also on those who do not. Patterns in Cambodia differ from those in more prosperous countries, but have parallels with other low-income countries. The authors suggest that much more attention is needed to the dynamics and impact of shadow education, including relationships between actors and the values that shadow education transmits as part of the hidden curriculum.